Aeroelastic flutter control of a bridge using rotating mass dampers and winglets

2020 ◽  
Vol 26 (23-24) ◽  
pp. 2185-2192
Author(s):  
Kamal K Bera ◽  
Naresh K Chandiramani
Keyword(s):  
Angular Speed ◽  
Fixed Number ◽  
Control Input ◽  
Vertical Force ◽  
Flat Plates ◽  
Aeroelastic Flutter ◽  
Continuous Rotation ◽  
Rational Function Approximation ◽  
Number Of Cycles ◽  
The Time Domain

Flutter control of a bridge deck section using a combination of aerodynamic and mechanical measures, that is controllable winglets and rotating mass dampers, is considered. Deck and winglets are considered as flat plates for their aerodynamics. Self-excited wind forces are represented in the time domain using the Scanlan–Tomko model with Roger’s rational function approximation for flutter derivatives. Winglet rotation relative to the deck is the control input generated by the variable-gain output feedback controller that uses vertical and torsional displacements of the deck as measured outputs. Control using winglets enhances the critical speed to twice the uncontrolled flutter speed. Further attenuation of vertical response is obtained by using rotating mass dampers configured to provide only a resultant vertical force due to counter-rotating unbalanced masses. The rotors are driven at a constant angular speed, and start–stop criteria are applied. This generates additional vertical force on the deck that is mostly out of phase with its vertical velocity. It yields better control than the damper operated in a continuous rotation mode for a fixed number of cycles. A maximum reduction of 15% in root mean square vertical response is obtained when compared with control using winglets only.

Kinematic Mechanics Analysis of Takeoff in Pre-Jumping for Sports Aerobics

2014 ◽  
Vol 1014 ◽  
pp. 157-160 ◽  
Author(s):  
Zi Xin Zhu
Keyword(s):  
Influencing Factors ◽  
Mechanical Model ◽  
Angular Speed ◽  
The Body ◽  
Dynamics Analysis ◽  
Vertical Force ◽  
Bending Angle ◽  
Mechanics Analysis ◽  
Light Pole

Takeoff is important to a variety of difficult movements for sports aerobics. The paper analyzes the kinematic mechanics of takeoff in pre-jumping for the sport. It first discusses the importance of takeoff in sports aerobics, and finds that the mechanics theory can be utilized to analyze the forces produced in the process of takeoff. Then, the dynamics analysis of takeoff in pre-jumping is completed to reveal the change of the vertical force and expound the sports process from the aspect of mechanics. Subsequently, the body for the athlete is simplified a two-light-pole mechanical model. On the basis of this, the mechanics analysis of vertical force in pre-jumping is done to find the influencing factors for vertical force. The results show that the vertical force produced by the takeoff in pre-jumping suffers from the factors of the weight, length of leg, bending angle of knee, and angular speed of leg rotation, etc.

Control of First Order Systems With Bounded Input by Asymptotic Output Tracking With Fractional Regulators

2007 ◽  
Author(s):  
Rube´n Marti´nez ◽  
Israel Mazaira ◽  
Vicente Feliu
Keyword(s):  
State Feedback ◽  
Dynamic State ◽  
Control Input ◽  
Bounded Control ◽  
First Order ◽  
Output Tracking ◽  
The Time Domain ◽  
Rational Order ◽  
Bounded Input ◽  
System Time

In this paper, the control of first order systems by applying fractional regulators in the time domain with bounded input is presented. The design of the proposed fractional regulator, is based in the local asymptotic output tracking of linear systems with bounded control input by linear dynamic state feedback and the reduction of the system time response by the expansion of integer-order models to rational-order one.

Point-to-Point Positioning of Flexible Structures Using a Time Domain LQ Smoothness Constraint

1992 ◽  
Vol 114 (3) ◽  
pp. 416-421 ◽  
Author(s):  
S. P. Bhat ◽  
D. K. Miu
Keyword(s):  
Time Domain ◽  
Finite Time ◽  
Flexible Structures ◽  
Control Input ◽  
Time Control ◽  
Smoothness Constraint ◽  
Point Control ◽  
Point To Point ◽  
The Time Domain ◽  
Different Order

An analytical procedure to implement optimal smoothing of the finite-time control waveform for point-to-point control problem is presented, which minimizes an optimality constraint consisting of a linear combination of the quadratic norms of its time derivatives. It is shown that the resulting control input is essentially the minimum norm solution augmented to satisfy some additional continuity requirements in the time domain. Application of the proposed technique to finite-time maneuvering of flexible structures is experimentally demonstrated and performances are compared using control torques evaluated based on different order of the smoothness constraint and order of the truncated plant model.

scholarly journals Edge Mostar Indices of Cacti Graph With Fixed Cycles

2021 ◽  
Vol 9 ◽  
Author(s):  
Farhana Yasmeen ◽  
Shehnaz Akhter ◽  
Kashif Ali ◽  
Syed Tahir Raza Rizvi
Keyword(s):  
Upper Bound ◽  
Connected Graph ◽  
Thermodynamic Characteristics ◽  
Chemical Compounds ◽  
Fixed Number ◽  
Common Vertex ◽  
Topological Invariants ◽  
Cactus Graph ◽  
Number Of Cycles

Topological invariants are the significant invariants that are used to study the physicochemical and thermodynamic characteristics of chemical compounds. Recently, a new bond additive invariant named the Mostar invariant has been introduced. For any connected graph ℋ, the edge Mostar invariant is described as Moe(ℋ)=∑gx∈E(ℋ)|mℋ(g)−mℋ(x)|, where mℋ(g)(or mℋ(x)) is the number of edges of ℋ lying closer to vertex g (or x) than to vertex x (or g). A graph having at most one common vertex between any two cycles is called a cactus graph. In this study, we compute the greatest edge Mostar invariant for cacti graphs with a fixed number of cycles and n vertices. Moreover, we calculate the sharp upper bound of the edge Mostar invariant for cacti graphs in ℭ(n,s), where s is the number of cycles.

Aerodynamics of Flapping Flight with Application to Insects

1951 ◽  
Vol 28 (2) ◽  
pp. 221-245 ◽  
Author(s):  
M. F. M. OSBORNE
Keyword(s):  
Power Plants ◽  
Insect Flight ◽  
The Body ◽  
Specific Power ◽  
Vertical Force ◽  
Flat Plates ◽  
Force Coefficients ◽  
Wing Motion ◽  
Lift And Drag ◽  
Geometrical Dimensions

1. General formulae are derived giving the lift, thrust and power when the wing motion is specified. The formulae are applied to twenty-five insects for which quantitative data are available. Average values for lift and drag coefficients, CL and CD, are derived by equating the weight to the vertical force and the thrust to the horizontal drag of the body. 2. The large drag and lift coefficients obtained for insect flight are attributed to acceleration effects. There is a distinct correlation between (C2L,+ C2)D)½ and the ratio of the flapping velocity of the wings to the linear velocity of flight. When this ratio and therefore the accelerations are small, the force coefficients do not exceed those to be expected for flat plates. Owing to the nature of the assumptions and approximations made, the values derived for CD, CL and CD/CL are minimum values. 3. Other characteristics of insect flight are discussed. In general, insects fly in such a way as to minimize the mechanical power required. In most, but not all cases, the useful force is the one perpendicular rather than parallel to the relative wind. The wing tips should move in a figure 8, the down beat should be slower than the up beat, and the majority of the necessary force must be supplied on the down beat. 4. Figures are given using the data from the twenty-five insects considered, showing average relations between power, specific power, mass, acceleration forces, force coefficients and geometrical dimensions. The power per gram, the ‘wasted power’, and the force coefficients all increase as the importance of the acceleration forcesincreases. 5. When plotted as functions of mass, quantities involving the power show much less dispersion than quantities involving the geometrical dimensions. This is taken to mean that despite the diversity of insect form, as ‘power plants’, they are all essentially similar. 6. A table of the observed or adopted flight parameters (frequency of beating, mass, wing area, velocity of flight, amplitude and orientation of wing motion) is appended.

scholarly journals Cyclic Fatigue Comparison of TruNatomy, Twisted File, and ProTaper Next Rotary Systems

2020 ◽  
Vol 2020 ◽  
pp. 1-4
Author(s):  
Abdullah Mahmoud Riyahi ◽  
Amr Bashiri ◽  
Khalid Alshahrani ◽  
Saad Alshahrani ◽  
Hadi M. Alamri ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Fatigue Resistance ◽  
Fatigue Testing ◽  
Clinical Performance ◽  
Cyclic Fatigue ◽  
Tooth Structure ◽  
Multiple Comparison Test ◽  
Continuous Rotation ◽  
Number Of Cycles ◽  
Cycles To Failure

TruNatomy (TN; Dentsply Sirona, Maillefer, Ballaigues, Switzerland) is a newly released system that was not tested in any previous studies. The objective of this work is to evaluate cyclic fatigue resistance of the new file and compare it with the Twisted Files (TF) and ProTaper Next (PTN). Forty-five files were distributed into 3 groups: PTN X2 (size 25 and taper 0.06), TF (size 25 and taper 0.06), and TN prime file (size 26 and taper 0.04). Each group included 15 files. Lengths of all files were 25 mm. Cyclic fatigue testing was done using artificial stainless-steel canals with 60-degree curvature and 5 mm radius. Continuous rotation movement at 300 rpm was used until the file fractures. Time for file separation was recorded in seconds. The number of cycles to failure (NCF) mean and standard deviation for each group was calculated. For statistical analysis of data, ANOVA and Tukey’s multiple comparison test were used. Mean and standard deviation (SD) of NCF were 259 ± 37.2, 521.67 ± 63.07 and 846.67 ± 37.16 for PTN, TF, and TN respectively. TN on average had significantly the highest NCF compared with PTN (p<0.05) and TF (p<0.05). TruNatomy file showed superior cyclic fatigue resistance. With its potential to preserve tooth structure, this file offers a good cyclic fatigue advantage. However, future studies are required to evaluate other properties of this file and to examine its clinical performance.

scholarly journals Correlation between Thermal Behaviour of AA5754-H111 during Fatigue Loading and Fatigue Strength at Fixed Number of Cycles

Materials ◽  
2018 ◽  
Vol 11 (5) ◽  
pp. 719 ◽  
Author(s):  
Rosa De Finis ◽  
Davide Palumbo ◽  
Livia Serio ◽  
Luigi De Filippis ◽  
Umberto Galietti
Keyword(s):  
Fatigue Strength ◽  
Thermal Behaviour ◽  
Fatigue Loading ◽  
Fixed Number ◽  
Number Of Cycles

scholarly journals An Erdős-Ko-Rado Theorem for Permutations with Fixed Number of Cycles

10.37236/4071 ◽  
2014 ◽  
Vol 21 (3) ◽  
Author(s):  
Cheng Yeaw Ku ◽  
Kok Bin Wong
Keyword(s):  
Positive Integer ◽  
Fixed Points ◽  
Fixed Number ◽  
Stirling Number ◽  
Disjoint Cycles ◽  
Set Of Permutations ◽  
Common Cycles ◽  
Number Of Cycles ◽  
Positive Integers

Let $S_{n}$ denote the set of permutations of $[n]=\{1,2,\dots, n\}$. For a positive integer $k$, define $S_{n,k}$ to be the set of all permutations of $[n]$ with exactly $k$ disjoint cycles, i.e.,\[ S_{n,k} = \{\pi \in S_{n}: \pi = c_{1}c_{2} \cdots c_{k}\},\] where $c_1,c_2,\dots ,c_k$ are disjoint cycles. The size of $S_{n,k}$ is $\left [ \begin{matrix}n\\ k \end{matrix}\right]=(-1)^{n-k}s(n,k)$, where $s(n,k)$ is the Stirling number of the first kind. A family $\mathcal{A} \subseteq S_{n,k}$ is said to be $t$-cycle-intersecting if any two elements of $\mathcal{A}$ have at least $t$ common cycles. In this paper we show that, given any positive integers $k,t$ with $k\geq t+1$, if $\mathcal{A} \subseteq S_{n,k}$ is $t$-cycle-intersecting and $n\ge n_{0}(k,t)$ where $n_{0}(k,t) = O(k^{t+2})$, then \[ |\mathcal{A}| \le \left [ \begin{matrix}n-t\\ k-t \end{matrix}\right],\]with equality if and only if $\mathcal{A}$ is the stabiliser of $t$ fixed points.

Flutter Suppression of Bridge Deck Section Using Controllable Winglets Driven by LQR Control

2017 ◽  
Author(s):  
K. K. Bera ◽  
N. K. Chandiramani
Keyword(s):  
Degrees Of Freedom ◽  
Bridge Deck ◽  
Pole Placement ◽  
Control Input ◽  
State Variables ◽  
Flat Plates ◽  
Flutter Suppression ◽  
Lqr Control ◽  
Full State Feedback ◽  
Trial And Error Method

Active flutter control of bridge deck section using controllable winglets is studied. Self-excited wind forces acting on deck and winglets are modeled using the Scanlan-Tomko model. Vertical, lateral and torsional degrees of freedom are considered for deck and corresponding eighteen experimental flutter derivatives (FD) are used. Winglets are modeled as flat plates and FDs are obtained from Theodorsen functions. Time domain formulation using Rogers rational function approximation leads to divergence speed much lower than the actual one, which is confirmed by Quasi steady theory. Hence, for control study, the usual trial and error method involving sweeping through speed and frequency is used. Rotations of winglets relative to deck are considered as control input, rather than the driving torque. Full state feedback with LQR control is applied. The state variables are estimated by designing a full order observer system using pole placement technique. Winglet rotations being restricted within bounds, the flutter behavior is studied using closed loop responses and compared with eigenvalue analysis. Numerical results shows the implemented control strategy is quite effective in flutter suppression and enhancing the flutter speed.

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